In previous electrophysiological studies I have established that olfactory and gustatory receptors of channel catfish, Ictalurus punctatus, are highly sensitive to amino acids and derivatives and have similar concentration-response functions. However, the two systems differ primarily by having different acid specificities. In this project I will examine the peripheral neural organization for the transfer of amino acid information to second order neurons. This will lead to a better understanding of the physiological distinctions between taste and smell and may offer some insight into stimulus and coding mechanisms. Multiunit and single unit taste recordings from the facial, glossopharyngeal and vagal cranial nerves will determine the classes and response properties of the amino acid fiber types present. Cross-adaptation studies will selectively adapt these systems to specific amino acids and derivatives. This will be informative about similarities among stimuli and between systems in the transduction mechanisms leading to the neural response and may provide information concerning specific membrane receptor sites. The chemo-specificity and response properties of second order olfactory units will be compared to simultaneously recorded receptor responses which will be informative about the central processing of primary olfactory information. Finally, the characteristics of the gustatory neural control of pancreatic endocrine secretion will be determined.